The present invention claims priority based on Argentina Patent Application Serial No. P99/01/01670, filed Apr. 12, 1999 and P99/01/02911, filed Jun. 17, 1999
The present invention relates generally to a steering mechanism assembly for automotive vehicles, and more particularly to rack and pinion steering mechanisms.
An important requirement for steering mechanisms for automotive vehicles, particularly pinion-rack bar power-assisted mechanisms, is offering stable steering means with precise movement between a pinion and a rack bar. This may be accomplished by providing a proper gear teeth assembly with proper contact points. This is achieved by mounting the components within established limits of tolerances. Sometimes, the tolerances vary out of established limits during the manufacturing process and to create an undesirable clearance between the gear teeth. Commonly, the correction usually involves additional complicated and time-consuming operations.
Moreover, the steering gear teeth are subject to wear over the life of the vehicle. The wear may adversely affect the assembly relationship since clearance between the teeth creates undesirable noises and improper alignment of vehicle relative to the steering wheel.
Undesirable operation of pinion-and-rack bar set is obtained when teeth are worn out. Wear is created by axial stresses present in the articulations of the steering housings. These stresses tend to urge the rack into a position distant from and out of proper assembly with the pinion. Thus, these stresses create a force opposed to maintaining the pinion and rack bar teeth in tight engagement.
The above cited teeth clearance is usually solved or compensated for by applying a force to a pinion roller bearing and rack bar and dampening by using an adjustment washer and pushing spring to urge the pinion and rack bar together for a proper assembly relationship.
Proper alignment and adjustment during manufacturing process of this mechanism, as well as wear corrections of the assembly between pinion and rack bar, is difficult in the prior known method.
Also, the source of the problem is hard to determine and sometimes requires the replacement of the complete steering unit.
It would therefore be desirable to improve the assembly relationship between teeth of said pinion-and-rack set. More particularly, it would be desirable to provide an adjustable assembly between the teeth for reducing bothersome noises and the above-mention knocking effects.
One object of the present invention is to improve the above cited pinion-rack bar mechanisms to enable adjustment of the relative position of teeth gears of the pinion-and-rack bar assembly in a fast and easy manner.
Another object of the present invention is to provide a novel pinion assembly of a steering mechanism that allows a periodical adjustment of pinion-rack bar assembly relationship so that the rotational movement of steering wheel is converted into reciprocal linear movement of rack which results in reduced effort with reduced steering.
Another object of the present invention is to provide a steering mechanism that allows selectively adjustable assembly of pinion-rack bar set inside a pinion casing integral to rack bar casing. The angular shifting of the mechanism avoids an excessive clearance in the pinion-rack bar assembly and allows a radial placement of the pinion for a proper transmission movement. Improper variations of the pinion clearance act against a uniform assembly relationship.
In one aspect of the invention, a tubular sleeve or bushing is positioned inside the casing that is fixed to rack bar casing. The cylindrical outer surface of the bushing is concentric and coaxial to the pinion casing. The inner surface of the bushing is eccentric. The tubular sleeve or bushing is capable of being radially moved in response to angular shifting of the bushing inside the casing to achieve a proper positioning of pinion and rack bar teeth by adjusting the eccentricity of the bushing outer surface relative to the pinion.
In another aspect of the invention, a tubular sleeve or bushing having an outer surface eccentric with regard to a rack casing has an upper end flange for manually or mechanically varying its outer eccentricity. It is also provided with an inner end nut for fixing it in a proper position against the casing. At the same time the rack is engaged to the pinion, an outer elastic buckling seal for resting against the inner concentric surface of the tubular sleeve or bushing absorbs eccentricity differences of the bushing when it is rotated for compensating for preloading the pinion and for assembly differences and for maintaining the rack in contact against the concentric inner surface.
One feature of the present invention is to provide improvements in steering mechanism casings offering the possibility of positioning the pinion by a simple angular displacement of a tubular sleeve or bushing when excessive clearance in the assembly relationship is detected due to teeth wear effects or manufacturing assembly failures.
The present invention is related to improvements in a steering mechanism casing for obtaining a proper adjustment in the assembly relationship between pinion and rack bar of the mechanism. In order to achieve the goal, a novel assembly with new improved characteristics is proposed for the pinion inside the casing. By using the proposed invention the pinion may be fixed to the torque bar of vehicle""s steering column in an assembly relationship with the rack bar.
This assembly allows a selective regulation of pinion axial positioning with regard to the rack bar and in response to teeth improper clearance generated by deficient adjustment during assembly of the casing or by a functional wear effect on the assembled means, thus compensating assembly differences and avoiding undesirable pounding effects on steering command during driving.
The adjustment is achieved by incorporating a bushing or sleeve telescopically assembled inside the casing and fixed to the rack bar casing with free angular clearance. The bushing has an upper flange for resting on the upper edge of the rack, and an outer thread in its lower edge for a roller nut against the lower edge for fixing the bushing in a proper position.
The bushing or tubular sleeve has a cylindrical outer surface coaxial to the rack inner surface, and an inner surface eccentric with regard to the outer surface of the bushing that delimits a movement area of a tubular retention and torsional supporting rack for the torque bar (pinion) end of vehicle""s steering column.
The lower end of the tubular rack is held or retained against a bushing or sleeve by a xe2x80x9cseegerxe2x80x9d type washer which avoids axial movements of the rack but allows angular displacements of same in response to torsional loading leaving the rack in contact to the eccentric surface of the bushing through end resilient buckling washers which allow a frictional contact with the surface.
By unscrewing the lower retention nut of the bushing an angular displacement of bushing is allowed and therefore the eccentricity of bushing inner surface could be varied transversely with regard to the axis of same, generating a repositioning movement of torque bar axis as well as a pinion approaching to rack bar thus obtaining a desired adjustment of teeth clearance.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.